Filter layer for photographic elements



tt f 3,050,393 Patented Aug. 2l, 1962 This invention relates to photographic materials which comprise a support and one ormore photographic emulsion layers and which include a colour filter layer.

In materials for colour photography it is usual to provide, coated on the support in succession, photographic emulsions adapted to record red, green and blue light respectively. However, silver halide emulsions always have some sensitivity to blue light so that it is necessary to locate, between the layer which is to record blue light and those which are to record red and green light, a layer which is absorptive of blue light. This may be a yellow dyestuff layer or a layer containing yellow colloidal silver. Further, if the layer intended to record red light has also some sensitivity to green, it is useful to include, between the green and red sensitive layers, a layer which is absorptive of green light, i.e. a magenta layer.

Since the presence of these filter layers would distort the colour rendering of the final processed colour image, the colour of the filter layers must be capable of ready removal or discharge. Where a yellow. colloidal silver layer is employed, for example, the usual step of removing developed silver from the material after the colour images have been formed therein, also removes the colloidal silver.

However, colloidal silver filter layers are not without their disadvantages since they have some tendency to interfere with the processing of the multilayer assembly. It is an object of the present invention to provide photographic materials containing filter layers wherein the filter layers contain dyestuffs which are readily discharged without departure from the usual processing techniques employed,

According to the present invention a photographic material comprises a support carrying one or more silver halide emulsion layers and a filter layer formed of a colloid containing a dye having the characteristic chromophoric structure "and being of the general formula R N=N--C('R )=NNHR where R and R are aromatic groups, e.g.-phenyl or naphthyl groups, or said groups containing nuclear substituents, and R is hydrogen, alkyl, substituted alkyl, aryl, aralkyl, hydroxy, carboxy or nitrile.

Preferred compounds are those in which R is phenyl, halophenyl, sulphophenyl or alkylphenyl, R is hydrogen or an alkyl group containing up to 4 carbon atoms, and R is phenyl, carboxyphenyl, alkylphenyl (the alkyl group containing up to 4 carbon atoms), or sulphonamidophenyl.

Suitable dyes are those known as formazan dyes, for a description of which reference may be made to Chemical Reviews, 1955, page 357. Dyes which contain two units of the chromophoric structure referred to above are included in this class.

More particularly according to the invention there is provided a photographic material comprising a support carrying three silver halide emulsion layers, one of which, being other than the middle layer of the three, is sensitive to blue light but is otherwise unsensitised, one of which is sensitive to green light, and one of which is sensitive to 2 red light, and a yellow filter layer located between said 'blue sensitive emulsion layer and the other emulsion layers, said yellow filter layer comprising a colloid material, preferably gelatin, containing a dye which has the chromophonic structure defined above and is yellow in colour.

According to a further feature of the invention there is provided a photographic material comprising a support carrying, in order, a silver halide emulsion layer sensitive to red light but partially sensitive to green light, a filter layer containing a magenta formazan dye which has the chromophoric structure defined above and is magenta in colour, a green sensitised silver halide emulsion layer, a filter layer containing a formazan dye which has the structure defined above and is yellow in colour, and finally blue sensitive silver halide emulsion layer.

It is preferred that the dye used should be non-migratory in the colloid, e.g. gelatin, in which it is present, so that it cannot wander freely from layer to layer. Many methods known in the art may be used, eg. the dye may be dissolved in a water-immiscible oil and dispersed in the form of fine droplets in the colloid medium, or the dye may advantageously include in its molecule a group or groups known to impart non-ditfusibility in a colloid medium, e.g. long chain alkyl groups such as stearyl groups. In this instance it is preferred that the dye also contains a solubilising group, e.g. a sulphonic or carboxylic acid group so that the dye may conveniently be dissolved as the ammonium or alkali metal salt for addition to the colloid.

The formazan dyes have excellent tinctorial power and so may be coated in thin colloid layers to give a high filter density. It is an advantage of the non-diffusible filter layers of this invention that their colour due to the said dyestutfs is rapidly and completely discharged by an alkaline potassium fern'cyanide bath which may be used (at the same time as one of the steps) in the removal of silver from colour processed materials. Accordingly, in use, they do not require the provision of any separate step to efiect discharge of the colour of the filter layer. It is believed that the discharge by such oxidising baths is due to the conversion of the coloured formazan dye to a corresponding colourless tetnazolium compound.

The following examples, in which the parts are by weight unless otherwise stated and temperatures are in C., will serve to illustrate the invention:

EXAMPLE 1 Preparation of the Insoluble Formazan Qt r 3.2 parts of o-chloraniline are suspended in 20 parts of water and 10 parts of concentrated hydrochloric acid. The amine is diazotised at 5 by the rapid'addition of 50 parts of an N/2 solution of sodium nitrite. The. diazo solution is added dropwise to a solution of 3.35 parts of acetaldehyde'phenyl hydrazone in parts of pyridine over 5 minutes at room temperature, 50 parts of Water are added and the dye precipitated is collected by filtration and washed with water to yield 5.82 parts of a reddish solid of M.Pt. 1

The dye I may be dispersed in gelation by any conventional means, e.g. a solution in ethyl acetate or other low boiling solvent may be added with a dispersing agent such as Aerosol OT to a gelation solution and homogenised. A coating of this dyed gel on film base on drying yields an orange-yellow layer which is rapidly dis- EXAMPLE 2 7 Preparation of the Soluble Formazan 5.0 parts of pure metanilic acid in 5.0 parts of water is dissolved by the addition of the minimum quantity of dilute sodium hydroxide solution. 712.5 parts of a 2 N aqueous solution of sodium nitrite is added and the mixture added dropwise to a solution of 10 parts of hydrochloric acid, and 10 parts of water at -5 The solution so obtained is added fairly rapidly to a solution of 3.5 parts 'of acetaldehyde phenyl hydrazone in 0 parts of pyridine. The dye is precipitated by the addition of concentrated hydrochloric acid, 75 parts, keeping the temperature below v20. The dye is collected by filtration, washed with dilute hydrochloric acid and then with acetone to give 6.35 parts of a'dark red solid. This solid is partially soluble in water, but dissolves readily in alkali 'to yield a deep yellow solution. Y

The dyellmay be coated in gelatin or silver halide emulsion in asimilar fashion to any other soluble dyestufi,'e.g. 1.0 part of the dye llsuspended in 100 parts of water is dissolved by the addition of 3 to 4 parts of a N solution'of sodium hydroxide. The solution is added to 200 parts of a solution of gelatin at 40, diluted as required and coated on film base or other. substrate to yield a yellow layer with 7x max 420 m 'Ihe'dye is rapidly washed out of the layer with water in ca 30 secs.

' In place of the dye II there may be used 3-cyano-1:5- di 2' carboxyphenylformazan, 3 carboxy 1:5 di phenylformazan, 1 4' sulphophenyl 3:5 diphenyl "formazan, or -3-phenyl-l:5-di-3-carboxyphenylformazan.

7 EXAMPLE 3 Preparation of an Insoluble Formazan Containing a Long Alkyl Chain 'prhydroxybenzaldehyde with dodecyl bromide and gives a low melting solid B.Pt. 1723/4 mm. A solution of the aldehyde in methanol is treated with an equimolecular amount of phenyl hydrazone to yield the aldehyde phenyl "hydrazone with white plates, M.Pt. 107;

j Aniline parts) in water (100 parts) and concentrated hydrochloric acid (50 parts) is diazotised at 5 by the addition of sodium nitrite (11 parts) in water (40 parts). The solution is made up to 250 parts with water. 40' parts of this solution are'run into 9.5 parts of the above p-dodecoxy benzaldehyde phenyl hydrazone dissolved in 200 parts of pyridine, the temperature being 'kept below The dye is filtered ofi and well Washed with water to yield 8-9 parts of a crystalline magenta solid of M.Pt. 100.

The dye 111 may be dispersed by any conventional means in gelatin and coated to yield a magenta layer with a broad absorption band max 525 mu. 7

In place of the dye III there may be used 1-4',-toly1-3- (4" dodecoxyphenyl) 5 phenylformazan, 3 undecyl 1:5 diphenylformazan, 1 phenyl 3 undecyl 5 (4' sulphonamidophenyl)formazan, or 1 phenyl 3 r undecyl-5-(1'-naphthyl)formazan.

EXAMPLE 4 Preparation of a Formazan Containing Groups Conferring Alkali Solubility and Non-Diflusibility 4-dodecylaniline-3-sulphonic acid sodium salt (4.5 pants) is dissolved in water (100 parts) and 25 parts of an aqueous N/ 2 sodium nitrite solution added. The solution at 30 is added dropwise to an ice cold solutionof concentrated hydrochloric acid (5 parts) and water (100 parts);

After stirring for 30 minutes the solid diazonium compound is collected by filtration and well washed free of nitrite and acid with ice-cold water. Thepaste is then added to'a solution of acetaldehyde-phenyl-hydrazone 1.7 parts) in pyridine (50 parts) and water (25 parts). The deep red solution is diluted with 500 parts of water and strongly acidified with concentrated hydrochloric acid at dye is non-difiusible. It is readily discharged in 10 secs. by immersion in a bath of V Parts Potassium ferricyanide 50 Sodium carbonate 10 Potassium bromide 10 Water to 1000 On washing, a clean colourless gelatin layer results which shows no tendency to reform colour on storage.

EXAMPLE 5 In place of the acetaldehyde phenyl hydrazone of Ex ample 4 there is used 2.5 parts of acetaldehyde-phenyl hydrazone Z-carboxylic acid to yield the dye V:

This dye shows a greater solubility than dye IV in aqueous alkaline solution. On coating in gelatin a non-diffusible layer A max 435 m is obtained. This discharges Example 4.

EXAMPLE 6 'In the place of the acetaldehyde phenyl hydrazone of Example 4 there is used 2.5 parts of acetaldehyde-phenyl hydraz one-3- or 4carboxylic. acid to yield similar valuable dyes. 5

similar to the dye of EXAMPLE 7 By the use of benzaldehyde phenyl hydrazone-Z-barboxylic acid in the method of Example 4 a dye is obtained which yields a reddish magenta layer A. max 500 run which possesses a subsidiary ultra-violet absorption. ('I'his reddish layer takes longer than the yellows of the Examples 4 to 6 to discharge, requiring of the order of 3-5 minutes.)

EXAMPLE8 CHHHQN HN-OSO NH; i 1'. SOBH I CH: (VI) A solution of 9.25 parts of 4-sulphonamidophenylhydrazine in 50 parts of ethanol is treated with 3.3 parts of acetaldehyde to give 7.6 parts of acetaldehyde-4-sulphonamidophenylhydrazine, M.Pt. 137. 2.7 parts of this product are dissolved in 75 parts of ethanol, 25 parts of water and 15 parts of normal sodium carbonate solution and coupled at 15 C. with the diazo paste obtained as in Example 4 from 4.5 parts of 4-dodecylaniline-3-sulphonic acid sodium salt. The reaction solution is diluted with 500 parts of water, the dyestutf potted out with 20 parts of crystalline sodium acetate and collected by filtration. The dye VI may be dispersed by conventional means in gelatin and coated to yield a yellow layer with A max 430 m EXAMPLE 9 By the method described in Example 4 the diazo paste from 4.5 parts of 4-dodecylaniline-3-sulphonic acid sodium salt is condensed with (a) 2.05 parts of acetaldehyde-ptolylhydrazone to give 5.3 parts of a yellow formazan dye, A max in gelatin 421 m (b) 2.21 parts of acetaldehyde-p-chlorphenylhydrazine to give 5.5 parts of a yellow formazan dye. This may be dispersed by conventional means in gelatin and coated to yield-a layer with A max EXAMPLE 10 By the method described in Example 4 the diazo paste from 4.5 parts of 4-dodecylauiline-3 -sulphonic acid sodium salt is condensed with (a) 1.85 parts of propionaldehydephenylhydrazone to give 4.6 parts of a yellow formazan dye, A max in gelatin 424 m (b) 2.02 parts of isobutyraldehydepheny-lhydrazone to give an orange red formazan dye. This may be dispersed by conventional means in gelatin and coated to yield a layer with A max 482 m EXAMPLE 11 t W0 N N a 4.5 parts of 4-dodecylaniline-2-sulphonic acid ammonium salt are dissolved in 100 parts of hot Water, 25 parts of an aqueous N/ 2 sodium nitrite solution added and the solution diluted with Water to 500 parts. The fine suspension so obtained at 50 is added dropwise to 10 parts of concentrated hydrochloric acid and 500 parts of water, the temperature being maintained at about 10. The solid diazo compound is collected by filtration and well washed free of nitrite and acid with ice-cold water. By the method described in Example 4 this diazo paste is coupled with 1.7 parts of acetaldehydephenylhydrazone to give 5.1 parts of a yellow formazan dye which when coated in gelatin gave a layer of A max 415 111/2.

taining 2.5 parts of sodium hydroxide at 10.

6 EXAMPLE 12 rapidly discharged in the alkaline ferricyanide bromide.

bleach bath described in Example 4 or in a solution of the following preferred composition:

, jParts Potassium ferricyanide 100 Potassium bromide -J 25 Sodium nitrate 20 Sodium carbonate monohydrate 20 Water to 1000 What I claim is:

1. A photographic material which comprises a support 4 carrying at least one silver halide emulsion layer and a filte'r layer formed of a colloid containing a dye of the general formula:

wherein X and Y are each selected from hydrogen, halogen, alkyl, alkoxy, sulphonic, sulphonylamido and carboxylic groups, and R is selected from hydrogen, alkyl and aryl groups.

2. A photographic material according to claim 1 wherein the dye is the compound of the formula:

N N 0 11 \C% 3. A photographic material according to claim 1 Wherein the dye is the compound of the formula-:

SOaH

References Cited in the file of this patent UNITED STATES PATENTS 2,231,684 'Schinzel Feb. 11, 1941 2,298,731 =Brooker et al. Oct. 13, 1942 2,647,833 Harrison et al. Aug. 4, 1953 OTHER REFERENCES Nineham: The Chemistry of Formazanes and Tetrazolium Salts, Chemical Reviews, vol. 55, pp. 355-483.

Glafkides: Photographic Chemistry, vol. 2, page 5 61, Foundation Press, London (1960); translation from the 2nd French edition. 

1. A PHOTOGRAPHIC MATERIAL WHICH COMPRISES A SUPPORT CARRYING AT LEAST ONE SILVER HALIDE EMULSION LAYER AND A FILTER LAYER FORMED OF A COLLOID CONTAINING A DYE OF THE GENERAL FORMULA: 